1. Field of the Invention
The present invention relates to the field of image sensors and imaging systems.
2. Description of the Related Art
Imaging systems, such as digital cameras, are used for still photography and video recording. The images captured by such systems may be used for viewing and/or further processing in a variety of representations, such as electronic, digital, or printed. A typical imaging system is built from a multiplicity of individual components that are integrated into a functional system.
FIG. 1 shows a schematic block diagram of an imaging system 100 of the prior art. System 100 has an electronic image sensor 102 that receives light through an optical interface 104. The optical interface may comprise a lens system, an aperture mechanism, and/or a light filter. Settings of the optical interface, e.g., zoom and aperture size, can be mechanically adjusted according to the user input using a motor 106.
The sensor may be implemented as a charge coupled device (CCD) or an array of complementary metal oxide semiconductor (CMOS) photosensitive circuits that generate electrical signals in response to the incident light. Analog signals from the sensor are converted by an analog-to-digital converter (ADC) 108 into digital image data and transferred for storage and/or further processing into a random access memory (RAM) 110. The data may be processed by a programmed processor 112 using algorithms stored in a read-only memory (ROM) 114. The processed image data may then be stored back to RAM 110 within system 100 and/or transferred to an external system, such as a personal computer, through interface 116 for storage as an electronic file and/or for further graphical and image processing, e.g., to enhance the image or for use with graphics software. The electronic components of system 100, such as sensor 102, ADC 108, memories 110 and 114, processor 112, and interface 116, are typically configured on a printed circuit board (PCB) 118.
Imaging systems, such as system 100, enable a user to manipulate mechanical buttons, knobs, toggle switches, etc., to select a few settings, most commonly, of the optical interface. However, many of the system features are often based on system software executed by processor 112. Suppliers of imaging systems, such as system 100 of FIG. 1, load the software into ROM 114 and select software-based feature settings for their imaging systems. Because cost-effective on-chip ROM is often made by the process of photomicrolithography and becomes a permanent part of the circuit design, such ROM cannot be modified once the product design is finished. This lack of flexibility of on-chip ROM makes it impossible to correct defects found later in the software, to add new features, or to use the imaging system for new purposes.